Adjustable contact structure for periodic switches



June 19, 1951 Q NELSON 2,557,197

ADJUSTABLE CONTACT STRUCTURE FOR PERIODIC SWITCHES Filed April 11, 1949 INVENTOR.

D. O. NELSON ATTORNEY Patented June 19,1951

ADJUSTABLE CONTA PERIODIC Donald 0. Nelson, Bendix Aviation a corporation oi CT STRUCTURE FOR SWITCHES Los Angeles, Calif., assignor to Corporation, Delaware South Bend, 11111.,

Application April 11, 1949, Serial No. 86,815

2 Claims.

This invention relates to sonic echo sounders oi the type in which an indicator (such as a lamp or a stylus) is moved continuously at a constant speed through a closed path, and a switch synchronized with the indicator movement closes a circuit to transmit a sonic pulse while the indicator is passing a predetermined point in its path, the echo of the pulse energizing the indicator to show its position at the time the echo is received. The indicator moves past a distance scale, and since the distance traversed by the indicator between the time of closure of the switch and the return of the echo is a measure 01' the depth, the switch closure must be accurately phased with respect to the indicator movement if the position of the indicator at the time of receipt of the echo is to be correctly shown by the scale.

An object of the invention is to provide a simple, reliable and easily and accurately adjustable switching mechanism for echo sounders of the type described.

Other more specific objects and features of the invention will become apparent from the description to follow.

Briefly, the switch construction of the invention comprises a drum, preferably of insulating material, that is mechanically coupled to the indicator for rotation in synchronism therewith, which drum has a helically extending conductive segment in its surface, in combination with one or more stationary brushes which ride on the drum so that each time the segment passes the brushes it momentarily completes a circuit theretions having a segment extending parallel to the drum axis. Howeve tangentially adjustable brushes are objectionable for the reason that the an appreciable area 01 contact with til thc'brushes have again worn to fit the drum. The iorcmentioucd detect prior devices is desirable for that reason.

In accordance with the present invention, the objectionable features of both Fig.4

the type illustrated.

Referring to Fig. 1, the depth sounder there depicted comprises a casing ll having a front door ll containing a window I! through which a 01' the recorder is visible.

Positioned in chart I! carries on one end a stylus II which is swept The instrument may be secured as tangential and gear which meshes with a spiral gear 28 on the I shaft on the recording arm H. The exact construction of the arm supporting and rotating members is not pertinent to the present invention.

Near its upper end, the shaft 24 is shown rotatably supported by a ball bearing 28, and above this bearing it has secured to it a drum 29. Above and beyond the drum 29 the shaft 24 is shown as carrying a spiral gear 30 which meshes with a spiral gear 3| on the drive shaft of a constant speed motor 32.

The drum 29 constitutes a part of the switch construction of the invention and is preferably formed of some hard insulating material except for a conductive segment 33 that extends helically thereacross, the surface of the segment being flush with the peripheral cylindrical surface of the drum. The drumcooperates with a pair of brushes 34 and 35 respectively which are secured to the ends of springs 35 which are supported by and extend from a brush support 39. Each spring 33 may have a longitudinal slot 36a therein through which screws 38 and 31 extend into the support 39, the support being of insulating material so as not toshort circuit the brush springs. To provide additional spring tension for urging the brushes against the drum second springs 40 may be pro- .vided overlying the springs 35 and adjustable by means of the screws 38. Lugs 42 on the ends of the springs 36 opposite the brushes may be provided for making electrical connection to the brushes. By loosening the screws 31,, the springs 36 and their associated brushes can be adjusted tangentially of the drum 29 for the purpose of adjusting the length of the transmitted pulse, as will be explained later.

The brush support 33 is supported for movement only in direction parallel to the drum 29. Thus it has a pair of holes 45 therein through which extend pins 43 which are anchored atone end to the frame 20. To adjustably move the brush support 39 axially of the drum 29 an adjusting screw 48 is shown having a threaded portion threaded through the support 39- and having an unthreaded portion 48a extending through a -hole provided therefor in the frame 20. Flanges 48b and 480 on the screw 48 engage the opposite faces of the frame 23 to prevent longitudinalmotion of the screw 48 in response to rotation thereof. sothat when the. screw is rotated the support 39 is moved in one direction or the other along the supporting pins 46.

Referrin to the schematic diagram of Fig. 4, the two brushes 34 and 35 are shown connected by leads 50 and 5| respectively to a transmitter 52 which is energized in response to interconnection of the brushes 34 and 35 by the contact segment 33 to develop a sonic pulse which is applied over conductors 53 and 54 to a transducer 55. The compressional wave transmitted by the transducer 55 is transmitted down through thewater to the bottom and reflected back to the transducer where it produces a corresponding electrical wave which is applied back over the conductors 53 and 54 to a receiver 58 which isconnected in multiple with the transmitter 52 across the conductors 53 and 54. The receiver may contain an amplifier and rectifier which applies a high potential pulse over a conductor 51 and a brush 58 to the arm I! and the stylus i8. As previously mentioned, the portion of the chart I3 that is traversed by the stylus I8 is supported by the conductive backing plate. It which may beconnected to ground and thereby complete a return circuit back to the receiver 55. The chart may be of a special paper which responds to the potential between the stylus l8 and backing plate IE to produce a mark on the paper.

It will be noted that the output of the transmitter 52 is applied not only to the transducer 55 but also to the receiver delivers a high voltage marking pulse to the 56 so that the latter stylus both at the time of transmission of the signal and at the time of reception of the echo.- Referring to Fig. 2, when the transmitted pulse is properly timed it produces a continuous line 60 along the upper edge of the scale on the chart i3, and the echo produces another line 6| which is spaced from the line 60 at any point a distance corresponding to the depth being measured.

When the zero adjustment is correct, the line 60 falls on the zero line of the scale on the chart. If the impulse is transmitted too soon, both the lines 60 and GI will be shifted upwardly so that they will not be properly coordinated with the chart scale. If the impulse is transmitted too late the lines 60 and BI will be downwardly displaced with respect to their proper positions on the chart scale. Accurate adjustment can be effected with the present invention by turning the adjusting screw 48 to shift the brush carrier 39 upwardly or downwardly and thereby vary the time when the two brushes are contacted by the helical segment 33. It will-be apparent that such adjustment does not alter the contact area between the drum 29 and the brushes 34 and 35.

It has been previously indicated that the length of the pulse transmitted can be varied by shifting one or the other of the brushes 3435 tan-- gentially with respect to the drum 29 by means of the clamping screws 31. With both brush springs 33 of substantially the same length, and the drum rotating clockwise (with'reference to Fig. 3) the segment 33 will contact the brush 34 before it contacts the brush 35 and will leave the brush 34 before leaving the brush 35. By making the spring of the brush 35 slightly shorter than the spring of brush 34, both brushes can be made to make and break with the segment 33 substantially simultaneously, under which condition the pulse will be of maximum length and determined by the width of the segment 33 and the corre sponding width of the brushes. By shifting either brush 34 or 35 tangentially relative to the other from the position of maximum contact, as described, the length of the pulse can be shortened to any desired extent, the limit being reached when the segment leaves one brush before contacting the next. These tangential adjustments of the brushes alter the contact area between the adjusted brush and the drum, which is objectionable for reasons previously mentioned.

- However, such adjustment need be made only at the time of installation and need not be disturbed- On the other hand, the adjustment thereafter. of the timing, which is accomplished by turning the screw 48, may have to be done at unpredict able intervals due to various factors, and it is highly desirable to be able to make this adjust-' ment without altering the contact areas of the brushes.

The present invention is equally applicable to depth recorders employing a stylus l8 as the indicating device and to sounders of the nonrecording type in which the indicator may be a a stylus for producing an indication on a record sheet, or a lamp or other device for producing a visible indication other than a mark on a chart.

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and I do not desire to be limited to the exact details shown and described.

I claim:

1. The switch construction comprising: a drum and means for rotating it, said drum having a cylindrical surface containing a contact segment extending helically in said surface; two brushes spaced from each other in the axial direction of the drum and bearing against said drum surface for periodically contacting said segment in response to rotation of the drum, and interconnecting the brushes only during simultaneous contact of both brushes with said segment; a support for said brushes; means supporting said brush support for movement parallel to the axis of said drum and against movement tangentially of said drum; means for adjustably moving said brush support parallel to the drum axis whereby the rotative position of the drum at the time of contact between said brushes and said helical segment can be varied without altering the contactangle between the brushes and the drum; and means supporting said two brushes on said support for relative tangential adjusting movement whereby the period of simultaneous contact of both brushes on said segment can be varied. 4

2. Apparatus according to claim 1 in which said brushes have substantially parallel front and rear edges extending parallel to the edges of said segment during contact therewith.

DONALD O. NELSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 741,365 Packard Oct. 13, 1903 1,793,989 Barr Feb. 24, 1931 1,948,253 Blondel Feb. 30, 1934 1,972,889 Hayes Sept. 11, 1934 1,983,254 Turner Dec. 4, 1934 2,098,266 Walker Nov. 9, 1937 

